Widening the Axion Window via Kinetic and St\"uckelberg Mixings

We point out that kinetic and St\"uckelberg mixings that are generically present in the low energy effective action of axions can significantly widen the window of axion decay constants. We show that an effective super-Planckian decay constant can be obtained even when the axion kinetic matrix has only sub-Planckian entries. Our minimal model involves only two axions, a St\"uckelberg U(1) and a modest rank instanton generating non-Abelian group. Below the mass of the St\"uckelberg U(1), there is only a single axion with a non-perturbatively generated potential. In contrast to previous approaches, the enhancement of the axion decay constant is not tied to the number of degrees of freedom introduced. We also discuss how kinetic mixings can lower the decay constant to the desired axion dark matter window. String theory embeddings of this scenario and their phenomenological features are briefly discussed.Comment: v2: published version (references and clarifying comments added); v1: 5 pages, 2 figure

Large Field Inflation from Axion Mixing

We study the general multi-axion systems, focusing on the possibility of large field inflation driven by axions. We find that through axion mixing from a non-diagonal metric on the moduli space and/or from St\"uckelberg coupling to a U(1) gauge field, an effectively super-Planckian decay constant can be generated without the need of "alignment" in the axion decay constants. We also investigate the consistency conditions related to the gauge symmetries in the multi-axion systems, such as vanishing gauge anomalies and the potential presence of generalized Chern-Simons terms. Our scenario applies generally to field theory models whose axion periodicities are intrinsically sub-Planckian, but it is most naturally realized in string theory. The types of axion mixings invoked in our scenario appear quite commonly in D-brane models, and we present its implementation in type II superstring theory. Explicit stringy models exhibiting all the characteristics of our ideas are constructed within the frameworks of Type IIA intersecting D6-brane models on T6/OR and Type IIB intersecting D7-brane models on Swiss-Cheese Calabi-Yau orientifolds.Comment: v2: references added, typos corrected; v1: 1+85 pages, 4 figure

Experiences of Stress and Coping over Time by Caregivers of Stroke Survivors: A Mixed-Methods Approach

Background/ Objectives: Caregivers of stroke survivors often experience physical and mental stress, decreased physical and emotional well-being, high burden of care, social isolation, and neglecting self-care. The majority of previous research studies have identified caregiver experiences during the first one-to-two years post stroke. Little is known about caregiver experiences beyond the first two years of the post- stroke recovery trajectory, indicating a need for longitudinal study of their experiences over time. Therefore, the objectives of this study were to 1) investigate caregiver experiences of stress and coping over 5-7 years post stroke using quantitative methods, and 2) explore through qualitative methods their stress and coping experiences over time and the concordance or divergence of qualitative and quantitative findings using a mixed-methods approach. Methods: This study was a secondary data analysis of a randomized clinical trial, CAReS (Committed to Assisting with Recovery after Stroke), between 2001-2005 and its follow-up study (between 2008-2010). A longitudinal follow up study was utilized to explore experiences of stress and coping over time by spousal caregivers of stroke survivors at baseline, 3, 6, 9, and 12 months post stroke and 5-7 years later. A mixed-methods, triangulated approach, the convergent QUAN-QUAL design, was used to obtain different but complementary data on caregiver stress and coping experiences over time. Results: Caregivers (N = 30) were primarily female (n =22, 73%) with a mean age of 58.8 and 33% were minorities. The range of mean perceived stress scores (PSS) was from 12.76-15.70 indicating caregivers experienced an average level of stress over time. The PSS scores gradually decreased with the lowest score at 5-7 years post stroke with a 1.54-point drop in PSS scores. However, the changes were small and not statistically significant (p = .32). The range of mean scores on the Family Crisis Oriented Personal Evaluation Scale (FCOPEs) was from 104.38 -119.93 implying spousal caregivers adopted multiple coping strategies. An inverse relationship between PSS and FCOPEs was statistically significant (p = .0069) indicating higher coping associated with lower perceived stress, and such relationship did not change over time (p = .8978). There was not a significant change over time in total coping scores (p = .53); however, a significant decrease over time was noted in two subscales – Acquiring Social Support (ASS) (p = .02), and Mobilizing Family Support (FBS) (p = .03). This finding was supported by qualitative data as caregivers noticed that social support gradually decreased over time. There was no significant change in PSS measurement over time, which is in agreement with the qualitative findings as four major categories of stress-related themes persisted through all stages of the stroke recovery trajectory. However, there were different sources leading to stress at different times. Their emotional stress evolved over time from struggling with the survivors’ personality changes, high caring demands, fear of recurrent strokes, unpreparedness and uncertainty of what the future would bring during the early stage of stroke recovery, to feeling lonely and sad about the loss of a supportive spousal relationship, and to suffering in silence and becoming more depressed for some caregivers at 3-6 months and 1 year post stroke, respectively. At 5-7 years post stroke, emotional stress was more related to the survivors’ depressive symptoms and fear of inability to fulfill the caring role due to their own declining health. Caregivers also expressed financial stress throughout all stages of stroke recovery. Common themes related to coping included: 1) religious and spiritual support with faith in God was utilized across all stages of the stroke recovery trajectory; 2) a problem-solving coping approach was more commonly adopted during early days of caregiving; 3) emotion-focused coping approach was consistently utilized over time as a way of relieving stress; 4) other coping strategies utilized all the time included being positive and grateful, and having a break from the caring situation in order to continue in caregiving role. Across semi-structured interviews, spousal caregivers reported a variety of sources of stress and coping behaviors. The majority of spousal caregivers that experienced a low stress level also reported a high score of coping measurement, indicating an agreement between qualitative and quantitative findings based on the reported stress and coping themes. Conclusions: Spousal caregivers continued to experience stress along with decreased social support as time progressed post-stroke, but these experiences evolved over time. Therefore, further research is needed to corroborate these findings and thus offer opportunities for researchers and clinicians to incorporate these findings to help spousal caregivers cope better at different stages of the stroke recovery trajectory